In　this　paper,　we　review　our　recent　works　about　optical　domain　modulation　modulated　microwave　signal　generation.　A　multi-format　switchable　microwave　signal　generator　using　a　single　dual-polarization　dual-parallel　Mach-Zehnder　modulator　is　proposed　and　demonstrated.　By　changing　the　modulation　state　of　the　modulator,　background-free　amplitude　shift　keying　(ASK),　phase　shift　keying　(PSK),　and　frequency　shift　keying　(FSK)　microwave　signals　can　be　generated.　The　background-free　arbitrarily　PSK　microwave　signals　can　be　transmitted　over　long　distances　without　power　degradation.　This　work　holds　great　promise　for　multifunctional　radar　and　communication　systems.　©　2022　IEEE.